I have no idea how relevant this might be or if this will resonate with anyone re: girls and their friends, but as I contemplate my dd navigating the world of middle school cliques this struck me:
http://www.npr.org/templates/transcript/transcript.php?storyId=133871975

GROSS: You have a couple of lines about cliques. Would you read that for us?

Ms. PEARSON: This is Petra reflecting on the fact that she has recently been admitted to queen bee Jillian's group with mixed consequences.

(Reading) You chose the kind of friends you wanted because you hoped you could be like them and not like you. To improve your image, you made yourself more stupid and less kind. As the months passed, the tradeoff for belonging started to feel too great, the shutting down of some vital part of yourself just so you could be included on the shopping trip into town, not have to sit on your own at lunch or have someone to walk home with.

Now, among friends, you are often lonelier than you had been before. The hierarchy of girls was so much more brutal than that of boys. The boys battled for supremacy out on the pitch, and after, they showered away the harm. The girls played dirtier. For girls, it was never just a game.